The control of blood pressure by the various reflexes of the cardiovascular system has been extensively investigated in lower animals. The results have been generalized to man. There is good evidence that many of the reflexes that have been studied in lower animals are not the same in the primate and therefore probably not applicable to man. The work which has been done in man does not permit the isolation of the receptor systems and therefore requires some assumptions to be made which may not be correct. The objective of this research proposal is to examine the role of the carotid, aortic and the cardiopulmonary receptors in the control of the cardiovascular system in the primate. Since the study will involve the conscious primate the results will not be clouded by the effects of anesthetics. It will also address the question of the specificity of the techniques of nonhypotensive hemorrhage and lower body negative and positive pressure as selectively effecting cardiopulmonary receptors. In order to more thoroughly address the question concerning the unloading of cardiopulmonary receptors, aortic and carotid nerve recordings will be done in the anesthetized monkey during nonhypotensive hemorrhages. After the reflexes have been examined in the conscious primate the interaction of the various reflexes will be studied. For sometime, it has been postulated that alternations in the arterial baroreflex mechanisms could result in a neurally mediated hypertension. This study will help to answer that question and help us understand the possible involvement of these receptors in pathologic conditions.